A group of death penalty opponents hold a vigil Tuesday, May 20, 2014, outside the prison where Missouri death row inmate Russell Bucklew was scheduled to be executed in Bonne Terre, Mo. U.S. Supreme Court Justice Samuel Alito has issued an order halting the planned execution of Bucklew scheduled for 12:01 a.m. Wednesday, but the order indicates that he or the high court will have more to say about the matter. (AP Photo/Jeff Roberson)

BONNE TERRE, Mo. (AP) — The U.S. Supreme Court weighed arguments Wednesday over whether a Missouri inmate’s rare vascular condition would cause him great suffering during what would be the nation’s first execution since last month’s botched case in Oklahoma.

Russell Bucklew had been scheduled to be put to death at 12:01 a.m. Wednesday for the 1996 killing of a man during a violent crime spree, but Supreme Court Justice Samuel Alito blocked the execution late Tuesday and the full court was considering the matter.

As the clock ticked Wednesday — by law, Missouri has a 24-hour window to carry out a scheduled execution — attorneys for Bucklew and the state parried in court filings about his medical circumstances.

Bucklew, 46, suffers from a rare congenital condition — cavernous hemangioma — that causes weakened and malformed blood vessels, as well as tumors in his nose and throat. His attorneys say this and the secrecy surrounding the state’s lethal injection drug combine to make for an unacceptably high chance of something going wrong during his execution. He told The Associated Press last week that he is scared of what might happen during the process.

During Oklahoma’s April 29 execution, inmate Clayton Lockett’s vein collapsed, and he writhed on the gurney before eventually dying of a heart attack more than 40 minutes after the start of a procedure that typically takes roughly one-fourth of that time to complete.

Mike O’Connell, a spokesman for the Missouri Department of Corrections, cautioned against reading too much into Alito’s intervention. Two of the six inmates Missouri has executed since switching to a single-drug system in November had appeals that stretched well into the state’s 24-hour window before the Supreme Court allowed the state to proceed. One of them was executed nearly 23 hours after he originally was scheduled to die.

In a 2-1 ruling Tuesday suspending the execution, an 8th U.S. Circuit Court of Appeals panel ruled that Bucklew’s “unrebutted medical evidence demonstrates the requisite sufficient likelihood of unnecessary pain and suffering beyond the constitutionally permissible amount inherent in all executions.” That was overruled later by the full court before Alito intervened.

If the Supreme Court rejects the appeal, Missouri would have until midnight to carry out the execution.

“The state does not have the right to inflict extreme, torturous pain during an execution,” Bucklew’s attorney Cheryl Pilate said. “We still hope that Mr. Bucklew’s grave medical condition and compromised airway will persuade the governor or a court to step back from this extremely risky execution.”

Bucklew won’t be getting help from Missouri Gov. Jay Nixon, a Democrat and death-penalty proponent who rejected Bucklew’s clemency request late Tuesday.

European companies opposed to capital punishment cut off supplies of certain execution drugs, leading Missouri and other states to turn to U.S. sources. The states refuse to identify the sources of their execution drugs, saying secrecy is necessary to protect the sources from possible retaliation by death penalty opponents.

Death penalty opponents say the secrecy makes it impossible to ensure that the drugs couldn’t cause an inmate to endure an agonizing death that rises to the level of unconstitutionally cruel and unusual punishment.

Missouri switched from a three-drug protocol to the single drug pentobarbital late last year. None of the six inmates executed since Missouri made the change has shown outward signs of pain or suffering.

The AP and four other news organizations filed a lawsuit last week against the Missouri Department of Corrections, claiming the state’s refusal to provide information on the execution drug violates the public’s constitutional right to have access to information about the punishment.

According to prosecutors, Bucklew was angry at his girlfriend, Stephanie Pruitt, for leaving him. Pruitt moved with her two daughters into the Cape Girardeau home of Michael Sanders, who had two sons. Bucklew tracked Pruitt down at Sanders’ home March 21, 1996, and killed Sanders in front of Pruitt and the four children. He handcuffed and beat Pruitt, drove her to a secluded area and raped her.

Later, after a state trooper spotted the car, Bucklew shot at the trooper but missed, authorities say. Bucklew was grazed in the head and hospitalized. He later escaped from jail, hid in the home of Pruitt’s mother and beat her with a hammer. She escaped, and Bucklew was arrested a short time later.